It is common practice to establish the position of a tool mounted in the spindle of a machining center by precisely positioning the cutting tool tip with respect to the tool holder. Assuming that a large number of tools are to be employed in a machining operation, such a tool setting procedure can become an onerous and time-consuming task. The prior art has recognized the need for some means to automatically establish the reference position of the tip or edge of a cutting tool when it is mounted in a machine. Examples of such tool setting devices may be founded in U.S. Pat. Nos. 3,143,041; 3,524,130; 3,704,641.
U.S. Pat. No. 3,524,130 shows a non-contact tool setting device while the other patents show contact tool setting devices. A disadvantage of tool setting devices of the above-noted patents is that there is no provision for efficiently controlling the velocity of the tool with respect to the tool setting device to insure rapid relative motion until the tool is proximate the setting device and thereafter a slower speed to prevent damaging a fragile and precisely contoured tool tip and provide for a more accurate reading. In order to provide for a rapid initial relative velocity in such tool setting devices, approximate information on tool position must be known. In addition, prior art tool setting devices which have incorporated linear variable displacement transducers have not included slide mounted engagement heads or members attached to the core rods so as not to impose any lateral forces on the core rods.